Command Line Option

This article describes built-in commands and its options


Invoke fluentd. Here is supported options:
Usage: fluentd [options]
-s, --setup [DIR=/etc/fluent] install sample configuration file to the directory`
-c, --config PATH config file path (default: /etc/fluent/fluent.conf)
--dry-run Check fluentd setup is correct or not
-p, --plugin DIR add plugin directory
-I PATH add library path
-r NAME load library
-d, --daemon PIDFILE daemonize fluent process
--no-supervisor run without fluent supervisor
--user USER change user
--group GROUP change group
-o, --log PATH log file path
-i CONFIG_STRING, inline config which is appended to the config file on-fly
--emit-error-log-interval SECONDS
suppress interval seconds of emit error logs
--suppress-repeated-stacktrace [VALUE]
suppress repeated stacktrace
--without-source invoke a fluentd without input plugins
--use-v1-config Use v1 configuration format (default)
--use-v0-config Use v0 configuration format
-v, --verbose increase verbose level (-v: debug, -vv: trace)
-q, --quiet decrease verbose level (-q: warn, -qq: error)
--suppress-config-dump suppress config dumping when fluentd starts
-g, --gemfile GEMFILE Gemfile path
-G, --gem-path GEM_INSTALL_PATH Gemfile install path (default: $(dirname $gemfile)/vendor/bundle)

Important options


Fluentd starts without configuration dump. If you don't want to show configuration in fluentd logs, e.g. don't show private keys, this options is useful.


If set true, suppress stacktrace in fluentd logs. Since v0.12, this option is true by default.


Fluentd starts without input plugins. This option is useful for flushing buffers with no new incoming events.

-i, --inline-config

If you use fluentd on XaaS which doesn't support persistent disks, this option is useful.


If you want to use your supervisor tools, this option avoids double supervisor.

Set via configuration file

Several options could be set via <system> directive configuration file. See configuration file article.


Send event to fluentd's in_forward/in_unix plugin. This is useful for testing.
Usage: fluent-cat [options] <tag>
-p, --port PORT fluent tcp port (default: 24224)
-h, --host HOST fluent host (default:
-u, --unix use unix socket instead of tcp
-s, --socket PATH unix socket path (default: /var/run/fluent/fluent.sock)
-f, --format FORMAT input format (default: json)
--json same as: -f json
--msgpack same as: -f msgpack
--none same as: -f none
--message-key KEY key field for none format (default: message)


Send json message with debug.log tag to local fluentd:
% echo '{"message":"hello"}' | fluent-cat debug.log
Send to other machine:
% echo '{"message":"hello"}' | fluent-cat debug.log --host testserver --port 24225
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.